# `Diffo.Provider.DefinedSimpleRelationship`
[🔗](https://github.com/diffo-dev/diffo/blob/v0.9.0/lib/diffo/provider/components/defined_simple_relationship.ex#L5)

Ash Resource for a relationship with an optional single embedded characteristic,
set at creation and never changed.

Extends `BaseRelationship` (source, target, type, timestamps). Optionally carries
one `DefinedCharacteristic` — a name/value pair stored directly on the Neo4j node.
The value is a `Diffo.Type.Primitive`, covering string, integer, float, boolean,
and temporal types.

Actions: **create** and **destroy** only. No update, no relate/unrelate. Once
defined, the characteristic is closed — that is the commitment.

Contrast with `Provider.Relationship` which allows mutable graph-based `Characteristic`
nodes to be added, removed, and updated over time.

`DefinedSimpleRelationship` is a general Provider primitive for any relationship
whose characteristic is a commitment or promise made at creation time.

An Ash Resource for a relationship with a single optional characteristic, defined at creation and closed thereafter

# `t`

```elixir
@type t() :: %Diffo.Provider.DefinedSimpleRelationship{
  __lateral_join_source__: term(),
  __meta__: term(),
  __metadata__: term(),
  __order__: term(),
  aggregates: term(),
  alias: term(),
  calculations: term(),
  characteristic: term(),
  created_at: term(),
  id: term(),
  source: term(),
  source_id: term(),
  target: term(),
  target_href: term(),
  target_id: term(),
  target_type: term(),
  type: term(),
  updated_at: term()
}
```

# `default_short_name`

# `input`

```elixir
@spec input(values :: map() | Keyword.t()) :: map() | no_return()
```

Validates that the keys in the provided input are valid for at least one action on the resource.

Raises a KeyError error at compile time if not. This exists because generally a struct should only ever
be created by Ash as a result of a successful action. You should not be creating records manually in code,
e.g `%MyResource{value: 1, value: 2}`. Generally that is fine, but often with embedded resources it is nice
to be able to validate the keys that are being provided, e.g

```elixir
Resource
|> Ash.Changeset.for_create(:create, %{embedded: EmbeddedResource.input(foo: 1, bar: 2)})
|> Ash.create()
```

# `input`

```elixir
@spec input(values :: map() | Keyword.t(), action :: atom()) :: map() | no_return()
```

Same as `input/1`, except restricts the keys to values accepted by the action provided.

# `primary_key_matches?`

---

*Consult [api-reference.md](api-reference.md) for complete listing*